1. Field
The present description relates to a method, system, and computer program for switching data in a communication fabric in a storage area network.
2. Description of Related Art
A storage area network (SAN) is frequently used to couple remote computer storage devices such as disk arrays, tape libraries, optical jukeboxes or other storage devices, to hosts in a manner which permits the storage devices to appear to the operating systems of the hosts as locally attached to the hosts. Fibre Channel (FC) is a high speed networking technology in which signals may be transmitted over various transmission media including fiber optic cable or twisted pair copper cables, for example.
In a Fibre Channel SAN, devices may be connected together in various topologies. For example, in Point-to-Point topology, devices may be connected directly together. In an Arbitrated Loop topology, devices may be connected in a loop or ring. In a switched fabric topology, the devices or loops of devices may be connected through Fibre Channel switches.
A Fibre Channel switch is a network switch compatible with the Fibre Channel protocol. A network switch is a computer networking device that connects together segments of a network. A network switch typically processes and routes data at protocol layers which includes at least the data link layer (layer 2 of the Open Systems Interconnection (OSI) model or layer FC1 of the Fibre Channel model, for example). Network switches that additionally process data at the network layer (layer 3 of the OSI model or layer FC2 of the Fibre Channel model, for example) and above are often referred to as multilayer switches.
A Fibre Channel switch allows the creation of a Fibre Channel fabric which is often a major component of many storage area networks. A Fibre Channel fabric typically includes a network of Fibre Channel devices, which allows many-to-many communication. Other features such as device name lookup, security, and redundancy are also often provided by such a network. Fibre Channel switches can implement “zoning” to disable unwanted traffic between certain fabric nodes.
A virtual storage area network (VSAN) is typically a collection of ports from a set of connected Fibre Channel switches, that form a virtual fabric. A port in Fibre Channel terminology is generally any entity that actively communicates over the network, and is not necessarily a hardware port. Such a port is usually implemented in a device such as disk storage, a device adapter on storage, a host bus adapter (HBA) on a server or a Fibre Channel switch. Multiple pairs of ports typically may communicate simultaneously in a fabric.
The use of VSANs allows traffic to be isolated within specific portions of the network. Thus, if a problem should occur in one VSAN, that problem can often be handled with a minimum of disruption to the rest of the network. VSANs usually can be configured separately and independently, as well.
Ports within a single Fibre Channel switch often can be partitioned into multiple VSANs, which can share hardware resources including hardware ports. Conversely, multiple switches typically can join a number of ports to form a single VSAN.
A VSAN, like each FC fabric, may offer different high-level protocols such as FCP (Fibre Channel Protocol), FCIP (Fibre Channel over Internet Protocol), FICON (Fiber Connection), and iSCSI (Internet Small Computer Systems Interface or Small Computer Systems Interface over TCP/IP (Transmission Control Protocol/Internet Protocol)), for example. Each VSAN may be a separate self-contained fabric having different features such as distinctive security policies, zones, events, memberships, and name services, for example. Traffic may also be separate in the different VSANs. Unlike a typical fabric that is resized switch-by-switch, a VSAN often may be resized port-by-port.
In addition to multi-layer switches such as a VSAN, a fabric may also include physical layer switches which provide user-configurable dedicated communication paths between respective ports. The physical layer refers to Layer 1 of the OSI or layer FC0 of the Fibre Channel model, for example. An example of a physical layer switch is an APCON “Intellapatch” physical switch.
A fabric may also include a debug device which performs trace capture and analysis, for example. Such a debug device is typically inserted at various points of the SAN to collect traffic samples. The Finisar “Xgig” device is an example of a debug device for storage area networks.